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ErikSchierboomBNAndrasIsaacGtasxatzial
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Add baffling-birthdays exercise (#2539)
* Add `baffling-birthdays` exercise * Update exercises/baffling-birthdays/introduction.md Co-authored-by: András B Nagy <20251272+BNAndras@users.noreply.github.com> * Update exercises/baffling-birthdays/introduction.md Co-authored-by: András B Nagy <20251272+BNAndras@users.noreply.github.com> * Consistency * Update instructions.md Co-authored-by: András B Nagy <20251272+BNAndras@users.noreply.github.com> * Update instructions.md Co-authored-by: Isaac Good <IsaacG@users.noreply.github.com> * Update introduction.md Co-authored-by: Isaac Good <IsaacG@users.noreply.github.com> * Update introduction.md Co-authored-by: Anastasios Chatzialexiou <16361161+tasxatzial@users.noreply.github.com> * Update introduction.md Co-authored-by: Isaac Good <IsaacG@users.noreply.github.com> * Lowercase birthday paradox * Use estimate * Out of college * Change birthday to birthdates * Add leap year note * Change quantity * Update exercises/baffling-birthdays/canonical-data.json Co-authored-by: Anastasios Chatzialexiou <16361161+tasxatzial@users.noreply.github.com> * Update exercises/baffling-birthdays/canonical-data.json Co-authored-by: Anastasios Chatzialexiou <16361161+tasxatzial@users.noreply.github.com> * Update exercises/baffling-birthdays/canonical-data.json Co-authored-by: Anastasios Chatzialexiou <16361161+tasxatzial@users.noreply.github.com> * Use collection instead of set * Estimate * Simplify instructions * Simplify canonical data * Update instructions.md Co-authored-by: Anastasios Chatzialexiou <16361161+tasxatzial@users.noreply.github.com> * Update instructions.md Co-authored-by: Anastasios Chatzialexiou <16361161+tasxatzial@users.noreply.github.com> * Another attempt * Tweaks * Update canonical-data.json Co-authored-by: Anastasios Chatzialexiou <16361161+tasxatzial@users.noreply.github.com> * Update canonical-data.json Co-authored-by: Anastasios Chatzialexiou <16361161+tasxatzial@users.noreply.github.com> * Use nesting and improve naming * More work * Merge properties * Update exercises/baffling-birthdays/canonical-data.json Co-authored-by: Anastasios Chatzialexiou <16361161+tasxatzial@users.noreply.github.com> * Update exercises/baffling-birthdays/introduction.md Co-authored-by: Anastasios Chatzialexiou <16361161+tasxatzial@users.noreply.github.com> * Update exercises/baffling-birthdays/instructions.md Co-authored-by: Anastasios Chatzialexiou <16361161+tasxatzial@users.noreply.github.com> --------- Co-authored-by: András B Nagy <20251272+BNAndras@users.noreply.github.com> Co-authored-by: Isaac Good <IsaacG@users.noreply.github.com> Co-authored-by: Anastasios Chatzialexiou <16361161+tasxatzial@users.noreply.github.com>
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‎exercises/baffling-birthdays/canonical-data.json

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{
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"exercise": "baffling-birthdays",
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"comments": [
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"Dates are formatted as 'YYYY-MM-DD'.",
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"",
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"To increase the likelihood of consistent result, the tests should run the code returning random results many times.",
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"",
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"The expected probability values should be compared using some tolerance to allow for small deviations."
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],
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"cases": [
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{
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"description": "shared birthday",
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"cases": [
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{
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"uuid": "716dcc2b-8fe4-4fc9-8c48-cbe70d8e6b67",
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"description": "one birthdate",
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"property": "sharedBirthday",
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"input": {
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"birthdates": ["2000-01-01"]
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},
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"expected": false
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},
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{
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"uuid": "f7b3eb26-bcfc-4c1e-a2de-af07afc33f45",
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"description": "two birthdates with same year, month, and day",
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"property": "sharedBirthday",
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"input": {
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"birthdates": ["2000-01-01", "2000-01-01"]
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},
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"expected": true
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},
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{
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"uuid": "7193409a-6e16-4bcb-b4cc-9ffe55f79b25",
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"description": "two birthdates with same year and month, but different day",
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"property": "sharedBirthday",
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"input": {
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"birthdates": ["2012-05-09", "2012-05-17"]
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},
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"expected": false
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},
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{
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"uuid": "d04db648-121b-4b72-93e8-d7d2dced4495",
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"description": "two birthdates with same month and day, but different year",
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"property": "sharedBirthday",
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"input": {
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"birthdates": ["1999-10-23", "1988-10-23"]
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},
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"expected": true
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},
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{
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"uuid": "3c8bd0f0-14c6-4d4c-975a-4c636bfdc233",
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"description": "two birthdates with same year, but different month and day",
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"property": "sharedBirthday",
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"input": {
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"birthdates": ["2007-12-19", "2007-04-27"]
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},
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"expected": false
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},
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{
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"uuid": "df5daba6-0879-4480-883c-e855c99cdaa3",
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"description": "two birthdates with different year, month, and day",
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"property": "sharedBirthday",
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"input": {
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"birthdates": ["1997-08-04", "1963-11-23"]
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},
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"expected": false
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},
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{
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"uuid": "0c17b220-cbb9-4bd7-872f-373044c7b406",
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"description": "multiple birthdates without shared birthday",
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"property": "sharedBirthday",
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"input": {
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"birthdates": [
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"1966-07-29",
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"1977-02-12",
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"2001-12-25",
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"1980-11-10"
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]
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},
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"expected": false
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},
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{
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"uuid": "966d6b0b-5c0a-4b8c-bc2d-64939ada49f8",
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"description": "multiple birthdates with one shared birthday",
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"property": "sharedBirthday",
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"input": {
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"birthdates": [
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"1966-07-29",
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"1977-02-12",
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"2001-07-29",
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"1980-11-10"
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]
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},
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"expected": true
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},
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{
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"uuid": "b7937d28-403b-4500-acce-4d9fe3a9620d",
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"description": "multiple birthdates with more than one shared birthday",
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"property": "sharedBirthday",
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"input": {
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"birthdates": [
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"1966-07-29",
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"1977-02-12",
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"2001-12-25",
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"1980-07-29",
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"2019-02-12"
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]
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},
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"expected": true
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}
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]
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},
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{
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"description": "random birthdates",
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"cases": [
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{
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"uuid": "70b38cea-d234-4697-b146-7d130cd4ee12",
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"description": "generate requested number of birthdates",
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"scenarios": ["random"],
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"property": "randomBirthdates",
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"input": {},
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"expected": "length == groupsize"
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},
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{
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"uuid": "d9d5b7d3-5fea-4752-b9c1-3fcd176d1b03",
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"description": "years are not leap years",
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"scenarios": ["random"],
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"property": "randomBirthdates",
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"input": {},
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"expected": {
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"years": {
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"leapYear": false
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}
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}
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},
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{
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"uuid": "d1074327-f68c-4c8a-b0ff-e3730d0f0521",
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"description": "months are random",
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"scenarios": ["random"],
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"property": "randomBirthdates",
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"input": {},
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"expected": {
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"months": {
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"random": true
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}
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}
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},
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{
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"uuid": "7df706b3-c3f5-471d-9563-23a4d0577940",
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"description": "days are random",
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"scenarios": ["random"],
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"property": "randomBirthdates",
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"input": {},
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"expected": {
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"days": {
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"random": true
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}
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}
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}
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]
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},
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{
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"description": "estimated probability of at least one shared birthday",
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"cases": [
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{
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"uuid": "89a462a4-4265-4912-9506-fb027913f221",
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"description": "for one person",
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"scenarios": ["random"],
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"property": "estimatedProbabilityOfSharedBirthday",
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"input": {
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"groupSize": 1
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},
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"expected": 0.0
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},
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{
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"uuid": "ec31c787-0ebb-4548-970c-5dcb4eadfb5f",
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"description": "among ten people",
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"scenarios": ["random"],
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"property": "estimatedProbabilityOfSharedBirthday",
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"input": {
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"groupSize": 10
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},
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"expected": 11.694818
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},
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{
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"uuid": "b548afac-a451-46a3-9bb0-cb1f60c48e2f",
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"description": "among twenty-three people",
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"scenarios": ["random"],
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"property": "estimatedProbabilityOfSharedBirthday",
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"input": {
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"groupSize": 23
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},
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"expected": 50.729723
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},
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{
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"uuid": "e43e6b9d-d77b-4f6c-a960-0fc0129a0bc5",
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"description": "among seventy people",
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"scenarios": ["random"],
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"property": "estimatedProbabilityOfSharedBirthday",
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"input": {
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"groupSize": 70
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},
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"expected": 99.915958
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}
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]
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}
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]
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}

‎exercises/baffling-birthdays/instructions.md

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# Instructions
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Your task is to estimate the birthday paradox's probabilities.
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To do this, you need to:
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- Generate random birthdates.
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- Check if a collection of randomly generated birthdates contains at least two with the same birthday.
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- Estimate the probability that at least two people in a group share the same birthday for different group sizes.
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~~~~exercism/note
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A birthdate includes the full date of birth (year, month, and day), whereas a birthday refers only to the month and day, which repeat each year.
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Two birthdates with the same month and day correspond to the same birthday.
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~~~~
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~~~~exercism/caution
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The birthday paradox assumes that:
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- There are 365 possible birthdays (no leap years).
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- Each birthday is equally likely (uniform distribution).
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Your implementation must follow these assumptions.
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~~~~

‎exercises/baffling-birthdays/introduction.md

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# Introduction
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Fresh out of college, you're throwing a huge party to celebrate with friends and family.
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Over 70 people have shown up, including your mildly eccentric Uncle Ted.
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In one of his usual antics, he bets you £100 that at least two people in the room share the same birthday.
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That sounds ridiculous — there are many more possible birthdays than there are guests, so you confidently accept.
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To your astonishment, after collecting the birthdays of just 32 guests, you've already found two guests that share the same birthday.
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Accepting your loss, you hand Uncle Ted his £100, but something feels off.
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The next day, curiosity gets the better of you.
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A quick web search leads you to the [birthday paradox][birthday-problem], which reveals that with just 23 people, the probability of a shared birthday exceeds 50%.
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Ah. So _that's_ why Uncle Ted was so confident.
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Determined to turn the tables, you start looking up other paradoxes; next time, _you'll_ be the one making the bets.
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~~~~exercism/note
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The birthday paradox is a [veridical paradox][veridical-paradox]: even though it feels wrong, it is actually true.
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[veridical-paradox]: https://en.wikipedia.org/wiki/Paradox#Quine's_classification
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~~~~
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[birthday-problem]: https://en.wikipedia.org/wiki/Birthday_problem

‎exercises/baffling-birthdays/metadata.toml

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title = "Baffling Birthdays"
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blurb = "Estimate the birthday paradox's probabilities."
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source = "Erik Schierboom"
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source_url = "https://github.com/exercism/problem-specifications/pull/2539"

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